A wide variety of powdered or granular products are conventionally packaged in bulk in relatively large flat bags which open along one edge. These bags are usually formed of a heavy paper, but sometimes they are formed of plastic material or include a plastic liner.
U.S. Pat. No. 5,279,095 describes a machine for opening flat bags of this type with two pairs of diverging endless belts, the belts of each pair rotating in opposite directions to advance the bags transversely therebetween. Apertures are provided in the belts and a partial vacuum drawn behind the opposing diverging portions holds each side of the bag against a respective working flight of the belt, separating the sides to open the bag while it is advanced. This design addresses a drawback with prior art machines which employed vacuum cups, the contact faces of which are subject to wear, thereby affecting the seal between the cup and the bag and reducing the reliability of operation. For high-speed operation of a machine employing diverging belts in this way, it would be advantageous that the opened bag be quickly and readily released from between the belts. Also, for improved reliability, maintaining positive gripping contact with the bag throughout its movement through the bag opening assembly would be preferable to relying upon the vacuum to support the weight of the bag. Furthermore, as the bags are advanced transversely between the belts (parallel to the opening end of the bags) this machine cannot present the separated sides of the opening end of each bag on opposing sides of a fill nozzle which projects through the opening end, ready for filling the bag. This therefore requires the additional complexity of provision for a fill nozzle able to extend into each empty bag and retract when the bag is full.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.